The answer to your question is "The U.S. is undermining an independence movement that is like the American Revolution." If you want more details feel free to ask me..
It means that the party the excerpt is talking about fears that the American ruling party action against the people`s desire for freedom and independence.
Explanation:
The spirits of 1776 are often identified as an intention to seek freedom, liberty independence and the ability to become responsible for their destiny. So the phrase states that the party in topic fear that the American Rulers try to stop that desire of freedom, liberty, and independence. Because that would take the power away from them, and the American Rulers will not want that. Suggesting that the party of concern likes that spirit and wishes it prevails in people, so they can act and take the power away from the Americans.
This is a fun one. The Roman Republic developed many inventions that helped better society. The roads for trade were huge that helped them get all the needs. Believe it or not, there was public health programs for better living. The legal system helped them from right and wrong.